In the food industry, diglycerides are becoming increasingly important as low calorie fatty materials. They can also be used to make specific triglycerides. Regiospecific triglycerides are important for making cocoa butter substitutes, low calorie fats and other tailored triglycerides. Esterification of glycerol with fatty acids using both chemical and enzymic (lipases) catalysts is difficult to control and frequently mixtures of monoglycerides and diglycerides are formed. Being hydrolytic enzymes, lipases require anhydrous conditions when used as the esterification catalysts. Otherwise, the reaction equilibrium will be driven towards hydrolysis. To overcome this limitation, a large excess of the acylating reagent (acid or ester) is used and the reaction products, such as water or alcohol, are being constantly removed. Another method involves irreversible esterification with active esters. Large excesses of the acylating reagents can be thus avoided but active esters are expensive.
Regiospecific diglycerides i.e., 1,3 diglycerides, are important not only for preparing regiospecific triglycerides but, as compounds in their own right Derivatives of monoglycerides are important in the food and drug industry Such derivatives include 1-alkyl-3-acyl glycerol, 1-lysophospholipid-3-acyl glycerol, glycerol glucolipids and 1-alkoxy-3-acyl glycerols. Lysophosolipids are used in foods and cosmetics.
To date, simple synthetic methods for introducing 1,3-functionality, i.e., a sugar, phosphate, sulfate, ether, etc. on a glycerol moiety have not been known. The majority of known procedures are multi-step processes and require protecting groups to discriminate among the primary and secondary hydroxy groups of glycerol. Such multi-step processes are not easily adapted to industrial synthesis.